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Sunrise And Sunset Times.

  • 13-01-2012 1:53pm
    #1
    200motels
    Registered Users, Registered Users 2 Posts: 2,604 ✭✭✭


    I was always wondering in my neck of the woods why in the first part of Dec the sun set so late in comparison to early Jan, there's nearly 20 mins of a difference yet the sun is in the same angle in the sky and conversely with the sunrise, in early Dec the sun rises earlier than early Jan. Why is this so? Surely if your 20 days before and after the solstice the sunset and sunrise times should be roughly the same. Anyone out there have a reason for this? I've google it and it still doesn't make it any clearer.


Comments

  • #2
    Rooy
    Registered Users, Registered Users 2 Posts: 863 ✭✭✭Rooy


    Was googling this myself before Christmas , I was looking at it from a different angle - that the evenings are getting brighter from about 10 days before the solaiste.

    Here are some useful links :

    http://earthsky.org/astronomy-essentials/everything-you-need-to-know-about-the-solstice-on-december-21


    and a bit more technical :

    http://curious.astro.cornell.edu/question.php?number=208

    hopefully you can relate this info to your questions!


  • #3
    200motels
    Registered Users, Registered Users 2 Posts: 2,604 ✭✭✭200motels


    Rooy wrote: »
    Was googling this myself before Christmas , I was looking at it from a different angle - that the evenings are getting brighter from about 10 days before the solaiste.

    Here are some useful links :

    http://earthsky.org/astronomy-essentials/everything-you-need-to-know-about-the-solstice-on-december-21


    and a bit more technical :

    http://curious.astro.cornell.edu/question.php?number=208

    hopefully you can relate this info to your questions!
    Thanks for that very interesting.


  • #4
    Elmer Blooker
    Registered Users, Registered Users 2 Posts: 6,185 ✭✭✭Elmer Blooker


    200motels wrote: »
    I was always wondering in my neck of the woods why in the first part of Dec the sun set so late in comparison to early Jan, there's nearly 20 mins of a difference yet the sun is in the same angle in the sky and conversely with the sunrise, in early Dec the sun rises earlier than early Jan. Why is this so? Surely if your 20 days before and after the solstice the sunset and sunrise times should be roughly the same. Anyone out there have a reason for this? I've google it and it still doesn't make it any clearer.

    I looked up www.timeanddate.com and I noticed that solar noon is at 1234 today and 1214 on Nov 29 (23 days before solstice compared to today which is 23 after) The length of each day is identical at 7h58mins. I think the answer is the time of solar noon and the fact that the clock is man made and has only been around for a few hundred years while the sun has rising and setting for many millions of years.


  • #5
    Calibos
    Registered Users, Registered Users 2 Posts: 7,810 ✭✭✭Calibos


    Due to the elliptical shape of the earths orbit around the sun and the fact that it speeds up a bit on the part of the ellipse close to the sun and slows down on the part furthest from the sun. (Earth is actually closet to the sun in Northern Winter and farthest from the sun during Northern Summer)

    This means that although the length of daylight starts increasing from the Winter Solstice onwards (ie the amount of time between Sunrise and Sunset starts increasing again), Sunrise continues to occur a little later each day for a few weeks after the solstice until that trend also reverses.


  • #6
    compsys
    Registered Users, Registered Users 2 Posts: 1,120 ✭✭✭compsys


    Calibos wrote: »
    Due to the elliptical shape of the earths orbit around the sun and the fact that it speeds up a bit on the part of the ellipse close to the sun and slows down on the part furthest from the sun. (Earth is actually closet to the sun in Northern Winter and farthest from the sun during Northern Summer)

    This means that although the length of daylight starts increasing from the Winter Solstice onwards (ie the amount of time between Sunrise and Sunset starts increasing again), Sunrise continues to occur a little later each day for a few weeks after the solstice until that trend also reverses.

    Also, the closer you are to the equator the more pronounced this is. Areas in the northern hemisphere but much further south (take Miami as an example) can have their earliest sunset as early as November with their darkest morning not until over a month later in January.


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